The present invention relates generally to integrated-circuit cases and more particularly to a case for carrying a substrate carrying an integrated circuit, wherein the substrate is fitted with contact areas suitable to provide electrical conducting connections between the integrated circuit and contact elements mounted on the case.
Contact connections between contact areas of a substrate and pins mounted outside an integrated circuit case for contacting the circuit on a printed-circuit board are conventionally implemented by bonding. Such a procedure however is complex and costly. Also such bonded contacts, when used for high frequency integrated circuits, can result in unpredictable high-frequency characteristics that can result in heat dissipation losses.
An object of the present invention is to provide a new and improved case of the above discussed type which provides a simpler contact arrangement and improved high-frequency signal coupling.
According to the present invention, an integrated circuit case for carrying an integrated circuit which is mounted on a substrate includes contact areas to establish electrical conducting contact with the integrated circuit. The case comprises contact elements for electrical connections to the contact areas. The contact areas are electrically connected to corresponding contact elements of the integrated circuit. The case includes an array of contact leads electrically connected to the case contact elements. The case contact elements are arranged to spatially coincide with the array of contact areas in such manner that free ends of the contact leads are arranged to contact the substrate contact areas. At least some of the contact leads have a coplanar lead structure of predetermined impedance.
Such a configuration offers the advantage that the impedance-controlled contact elements between the substrate and the case reduce power losses caused, for instance, by high frequency energy reflection at impedance discontinuities. Accordingly, there is a reduction in heat dissipation, i.e., less xe2x80x9cthermal stressingxe2x80x9d is attained. Thereby, integrated circuits operating at high clock rates, such as computer processors (CPUs), can be packaged into the case in a problem-free manner. The case is designed so conventional integrated circuits can be packaged in the case, enabling the case to be easily integrated in existing production facilities without causing problems.
Simple and economical installation of the integrated circuit into the case is attained by designing the case contact leads to be intrinsically dimensionally stable and flexible and by mounting them in such a way that, when the integrated circuit is mounted inside the case, the case contact leads contact corresponding contact areas of the substrate with appropriate contact pressures in order to establish the desired electrical contact. In using the case of the present invention, there is no need to establish each contact individually, in contrast to the prior art use of boned wires.
Optimal impedance matching, possibly with simultaneous impedance conversion, between the substrate contact areas and the contact elements on the case, is attained because the impedance of the coplanar contact leads at one end of an output impedance facing the substrate contact areas corresponds to the output impedance at the particular substrate contact areas with which contact is made. In addition, the impedance of the coplanar contact leads at one end facing the case contact elements corresponds to a printed-circuit board input impedance at the corresponding contact areas.
At least some of the case contact elements are preferably pins to affix a surface of the case to a printed circuit external to the case.
In a preferred embodiment of the invention, a dielectric slab supporting the coplanar lead structure is affixed to at least one coplanar lead structure across a predetermined segment between a free end of the contact element and the case contact elements on one or both sides of the case. The individual leads of the coplanar lead structure are configured between the dielectric and the contact element free end in such manner that the leads are supported in a resilient manner in the space or relative to the affixing dielectric.
A gap is subtended for the purpose of controlled impedance matching in such manner between two leads of at least one coplanar lead structure. This causes a predetermined wave impedance, which is constant or variable, to be provided between the contact element free end and the case contact elements. If a dielectric is used, the gap where the dielectric is located is commensurately wider than in the region where the coplanar lead structure does not have a dielectric.
In order to attain optimally screened and impedance-controlled contacting, the case contact elements are at least partly in the form of coaxial connectors to provide connection to a coaxial cable.
In an especially preferred embodiment of the invention, the coaxial connector is an angled connecting element which, at the case, electrically connects a particular coplanar lead structure to a coaxial waveguide. Such a coaxial connector comprises: (1) an adapter at the side of the coplanar structure to connect to a planar strip and (2) a coaxial adapter at the side of the coaxial array which can be connected to a coaxial line. The adapter on the coplanar structure side is connected within the outer circumference of the angled connecting element to an inner pin of the coaxial connector. The adapter at the coplanar structure side can also be in the form of a planar waveguide having a predetermined wave impedance. The adapter at the coplanar structure side is fitted with a dielectric substrate and a stripline. The inner pin of the coaxial connector is connected through the substrate to the stripline within a housing of the angled connecting element.
The substrate is preferably made of polytetrafluroethylene and the planar waveguide is preferably a microstrip line or a coplanar line. A screw or clamp fitting is appropriately present at the coaxial connector for fixedly mounting a coaxial line. Preferably the planar waveguide is mounted perpendicularly to the coaxial connector.
At least several of the contact areas are configured at least partly as a coplanar structure of leads to attain low transmission losses of high frequency signals coupled between the integrated circuit and the case contact elements.
The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed descriptions of several specific embodiments thereof, especially when taken in conjunction with the accompanying drawings.